Don't use file-based part-of when part files are shared.

sdk/lib/html/html_common/filtered_element_list.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of "html_common.dart";
+part of html_common;
 
 /**
  * An indexable collection of a node's direct descendants in the document tree,
  * filtered so that only elements are in the collection.
  */
 class FilteredElementList extends ListBase<Element> implements NodeListWrapper {
   final Node _node;
   final List<Node> _childNodes;
 
   /**
@@ skipping 126 matching lines @@
   }
 
   int get length => _iterable.length;
   Element operator [](int index) => _iterable.elementAt(index);
   // This cannot use the iterator, because operations during iteration might
   // modify the collection, e.g. addAll might append a node to another parent.
   Iterator<Element> get iterator => _filtered.iterator;
 
   List<Node> get rawList => _node.childNodes;
 }